Guarded electrical overstress protection circuit

Abstract

Disclosed embodiments are directed to an electrical overstress protection circuit. The electrical overstress protection circuit may include an intermediate node receiving a reference voltage, a first pair of clamp devices, having opposite polarity, clamping an input signal line to the intermediate node, and a second pair of clamp devices, each clamping the intermediate node to one of two reference potentials. The electrical overstress protection circuit may also include a filter connected to the intermediate node to reduce noise at the intermediate node.

We claim: 
     
       1. An electrical overstress protection circuit, comprising:
 a pair of clamp devices, having opposite polarity, connecting an input signal line to a common node; and 
 a second pair of clamp devices, each extending from the common node to a respective reference potential source, 
 wherein the common node is at an externally-supplied constant reference voltage. 
 
     
     
       2. The electrical overstress protection circuit of  claim 1 , wherein the clamp devices are diodes. 
     
     
       3. The electrical overstress protection circuit of  claim 1 , wherein the input data signal is a time-varying current signal. 
     
     
       4. The electrical overstress protection circuit of  claim 1 , wherein the input data signal is a time-varying voltage signal. 
     
     
       5. The electrical overstress protection circuit of  claim 1 , further comprising a plurality of input data signal lines, each data signal line connected to a plurality of clamping devices clamping each input signal line to the intermediate node. 
     
     
       6. The electrical overstress protection circuit of  claim 1 , further comprising a test circuit clamped to the intermediate node, the test circuit comprising a switch for connecting the test circuit to the intermediate node and a test signal input receiver for receiving a test input data signal. 
     
     
       7. The electrical overstress protection circuit of  claim 1 , further comprising an RC network extending from the reference voltage through the intermediate node to one of the first and second reference potentials. 
     
     
       8. The electrical overstress protection circuit of  claim 1 , wherein the externally-supplied constant reference voltage is supplied by an imaging chip reference voltage. 
     
     
       9. A data receiver including an electrical overstress protection circuit, comprising:
 an input signal line to receive an input data signal; and 
 a clamp circuit receiving an externally-supplied constant reference voltage at an internal node, the clamp circuit comprising:
 a plurality of clamp devices clamping the input signal line to the internal node, 
 a clamp device clamping the internal node to a first reference potential, and 
 a clamp device clamping the internal node to a second reference potential. 
 
 
     
     
       10. The data receiver of  claim 9 , further comprising: an RC network extending from the reference voltage through the intermediate node to the second reference potentials. 
     
     
       11. The data receiver of  claim 9 , wherein the externally-supplied constant reference voltage is selected to correspond to a DC component of the input data signal. 
     
     
       12. The data receiver of  claim 9 , wherein the clamp devices are diodes. 
     
     
       13. The data receiver of  claim 9 , wherein the input signal is a time-varying current signal. 
     
     
       14. The data receiver of  claim 9 , wherein the input signal is a time-varying voltage signal. 
     
     
       15. The data receiver of  claim 9 , further comprising: a plurality of inputs for receiving input data signals; and a plurality of clamping devices clamping each input signal line to the intermediate node. 
     
     
       16. The data receiver of  claim 9 , further comprising: a test circuit connected to the intermediate node. 
     
     
       17. The data receiver of  claim 16 , the test circuit comprising:
 a switch for connecting the test circuit to the intermediate node; and 
 a test signal outputting a test data signal. 
 
     
     
       18. The data receiver of  claim 9 , wherein the externally-supplied constant reference voltage is supplied by an imaging chip reference voltage. 
     
     
       19. The data receiver of  claim 9 , wherein the plurality of clamp devices clamping the input signal line to the internal node include at least a pair of clamp devices having opposite polarity. 
     
     
       20. An overstress protection circuit for an input signal line of an integrated circuit, comprising:
 a two-stage clamping circuit coupling the input signal line to a pair of reference potential sources, a first stage of the clamping circuit extending from the input signal line to an internal node and a second stage of the clamping circuit extending from the internal node to at least one reference potential, and 
 a signal source providing an externally-supplied constant reference voltage at the internal node. 
 
     
     
       21. The overstress protection circuit of  claim 20 , further comprising:
 a filter extending from the input signal line through the intermediate node to one of the first and second reference potentials. 
 
     
     
       22. The overstress protection circuit of  claim 20 , wherein the externally-supplied constant reference voltage is selected to correspond to a DC component of the input signal. 
     
     
       23. The electrical overstress protection circuit of  claim 1 , wherein the externally-supplied constant reference voltage is selected to correspond to a DC component of the input signal. 
     
     
       24. The overstress protection circuit of  claim 20 , wherein the two-stage clamping circuit includes at least a pair of diodes. 
     
     
       25. The overstress protection circuit of  claim 20 , wherein the input signal line carries a time-varying current signal. 
     
     
       26. The overstress protection circuit of  claim 20 , wherein the input signal line carries a time-varying voltage signal. 
     
     
       27. The overstress protection circuit of  claim 20 , wherein the signal source is a reference voltage from an imaging chip. 
     
     
       28. The overstress protection circuit of  claim 20 , wherein the first stage of the clamping circuit includes at least a pair of clamp devices where the devices having opposite polarity.